Rigid molds have long been used for making miscellaneous items. Typically, molds have a top part and a bottom part that maintain the flowable material to be molded into a particular shape in sandwiched relation therebetween. Accordingly, a seam is produced in the final product where the top and bottom mold parts come together.
Where an item to be produced has its greatest breadth at a region other than its top or bottom, the mold parts must be made so that the parting line between them coincides with that maximum breadth.
Although the present invention is not restricted to molds that produce sailboards (used in windsurfing) or surfboards, it was developed in that art as were many other developments in the mold making arts. For example, U.S. Pat. No. 4,255,221 to Young shows a pressure forming apparatus for making a surfboard. A sailboard manufacturing process is shown in U.S. Pat. No. 4,556,003 to Prade. A process for manufacturing a foam-filled article such as a surfboard is shown in U.S. Pat. No. 4,383,955 to Rubio et al. Surfboards and sailboards can also be made following the teachings and suggestions of U.S. Pat. Nos. 4,551,290 to Mizell and 4,173,032 to Frank.
While all of the known sailboard and surfboard making techniques produce articles having utility, there are a number of limitations in the art. One of the most important limitations involves time; it takes between thirty to forty-five hours to manufacture a professionally acceptable sailboard, for example. The known techniques also produce sailboards having a seam at the widest part thereof, i.e., due to the limitations of the rigid molds of the prior art, the production of a sailboard having no seam has been unattainable.
To manufacture a sailboard by following prior art techniques developed by the present inventor, a styrofoam blank having the general shape of a sailboard is employed as the starting material. The top of the styrofoam is cut away to form a recess; fiberglass saturated with epoxy is applied to the recess and a PVC foam inlay is inserted thereinto. The inlay is called the deck of the sailboard, because the windsurfer stands on the deck when windsurfing. Another layer of PVC foam is applied to the bottom of the styrofoam blank after first applying a layer of fiberglass saturated with epoxy to the bottom of the blank.
The PVC foam top and bottom pieces are held in place with brads or nails and the blank/PVC form assembly is placed in an air-tight bag. Weights are applied to the PVC foam pieces, the bag is vacuumed to the blank for a couple of hours, and the assembly is oven cured for three hours.
This vacuum bag technique creates flaws in the fiber orientation, due to the wrinkles that are formed by the bag. Since the fibers may be skewed by the wrinkles in the plastic, the boards produced by the above-described technique are flawed. Thus, not only are the techniques of the prior art very time consuming, the resulting sailboard has a seam at its greatest breadth and may have structural flaws as well due to the effects of the wrinkled plastic. Moreover, the low vacuums attainable by the above-described technique limit the strength of the sailboards produced thereby.